The present invention concerns a polymerization process for producing branched polyesters with characteristics especially useful in high solids paints.
Environmental and economic concerns often make it desirable to minimize the quantity of organic solvent released to the atmosphere in the application of paints, such as to automobiles, either in single color coats or in color coat/clear coat or other applications. One way to do this is to make a paint with higher solids content which contains less solvent to evaporate. Several properties must be balanced and reconciled in developing such a paint. Higher polydispersity polymers sometimes permit the preparation of higher solids paints, but it is necessary to keep the viscosity, rheology and other properties of the paint under control. Polydispersity is defined as the ratio of the weight average molecular weight, Mw, to the number average molecular weight, Mn. Polymers having higher Mw often make paints with higher viscosity unless the polydispersity is also high. Such high viscosities can make it more difficult to apply the paint by conventional techniques such as spraying.
It would be desirable to have polymers which can be used to make paints with relatively high solids content and low viscosity.